Method for positioning determinations of receivers

Abstract

The disclosed method and system is used to determine the position of a user device. The user device can receive data signals and/or carrier signals from orbiting space vehicles. These data signals can be used for positioning calculation and/or track maintenance of the user device. The disclosed method and system can account for time and frequency biases of the user device. For the track maintenance, a Kalman filter state estimator can be extended to include a velocity of the user device.

We claim: 
     
       1. A method for positioning calculations in an occluded environment comprising:
 receiving signals from at least one space vehicle; 
 computing a pseudo range and a pseudo range rate including a time bias and a frequency bias of the signals; and 
 minimizing a cost function including the pseudo range and the pseudo range rate to obtain a position. 
 
     
     
       2. The method of  claim 1 , wherein the cost function includes a product of the pseudo range and the pseudo range rate. 
     
     
       3. The method of  claim 1 , wherein computing the pseudo range and the pseudo range rate includes a nonlinear least squares method. 
     
     
       4. The method of  claim 1 , wherein computing the time bias and the frequency bias includes a linear least squares method. 
     
     
       5. The method of  claim 1 , wherein the time bias and the frequency bias are expressed as explicit functions of a position of a user device. 
     
     
       6. The method of  claim 1 , wherein expressions of the time bias and the frequency bias modify a cost function by removing the biases as independent states, thereby reducing the number of independent variables to those of a position of the user device alone. 
     
     
       7. The method of  claim 1 , wherein the signal is received from a LEO satellite. 
     
     
       8. The method of  claim 7 , wherein the LEO satellite is part of the Iridium system. 
     
     
       9. The method  claim 1 , wherein the occluded environment includes at least one of an indoor environment, a jamming environment, and other environment where the signal is degraded by incidental or deliberate radio frequency interference. 
     
     
       10. The method of  claim 1 , wherein obtaining the position of the user device is based on latitude and longitude information. 
     
     
       11. The method of  claim 5 , wherein the user device comprises:
 an antenna capable of receiving signals from at least one space vehicle; and 
 a computer system capable of processing the received signals to calculate a time bias and a frequency bias, the computer system using the time bias and the frequency bias to determine a position of the user device. 
 
     
     
       12. The method of  claim 11 , wherein the computer system can execute an extended Kalman filter state estimator including a velocity of the user device in order to estimate a position of the user device if the antenna does not receive the signals of the at least on space vehicle. 
     
     
       13. The method of  claim 11 , wherein the computer system further comprises an output device.